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Russian Geology and Geophysics

2001 year, number 10

Seismic tomography study of the Tien Shan crust

T. M. Sabitova and A. A. Adamova
Keywords: Seismic tomography, orogen, waveguide, geodynamics
Pages: 1543-1553

Abstract

This paper presents the characteristics of the first 3D velocity model of the Tien Shan crust, inferred from the traveltimes of P- and S-waves from local and regional earthquakes, recorded by seismic stations in Kyrgyzstan and adjacent regions. Seismic tomography imaging provided new data on the deep structure of the Tien Shan orogen.
Velocity section along the profile crossing source zones of five strong earthquakes (M 6) shows different structural types of the crust. We describe the peculiarities of the velocity structure of strong-earthquake zones and criteria for their distinguishing: waveguides, subvertical weakened channels, and high-velocity bodies to which the foci of strong events are confined.
We also give examples of geological and geophysical interpretation of the first velocity model and show its weakness. The necessity of new imaging is shown. For this purpose a data set was enlarged and described in detail. The principles of collection of data and calculation of a new model are also considered. Much attention was paid to calculation of a 1D model which is the basis for further computation of the new 3D model. Some preliminary results of 3D inversion for P-wave velocities are presented. We believe that the new model, describing the velocity structure of the Tien Shan in regional scale, will provide a more argued judgment about the geodynamic processes there.